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electrical:12v:alternator_charging_rates [2023/09/10 12:51] frater_secessus [TLDR] |
electrical:12v:alternator_charging_rates [2023/09/10 13:25] (current) frater_secessus [estimating combiner charging] |
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- | ====== How much will by battery charge by alternator? ====== | + | DRAFT |
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+ | ====== How much will my battery charge by alternator? ====== | ||
This should be easy, right? | This should be easy, right? | ||
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We know the time part because we're the ones driving. | We know the time part because we're the ones driving. | ||
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===== TLDR ===== | ===== TLDR ===== | ||
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* [[electrical: | * [[electrical: | ||
* charging with [[electrical: | * charging with [[electrical: | ||
- | * The charge rate will likely start off ≤0.33[[electrical: | + | * The charge rate will likely start off ≤0.33[[electrical: |
* the shape of the taper hinges chiefly on battery chemistry | * the shape of the taper hinges chiefly on battery chemistry | ||
* this unpredictablity is less important when [[electrical: | * this unpredictablity is less important when [[electrical: | ||
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Since current is a function of C, **bigger banks will pull more current than small ones**. | Since current is a function of C, **bigger banks will pull more current than small ones**. | ||
- | Banks will pull more current at lower states of charge and less current at higher states of charge. | + | Banks will **pull more current at lower states of charge** and less current at higher states of charge. |
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- | ==== charging | + | ===== estimating DC-DC charging ===== |
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+ | DC-DC charging rates are more predictable because of how they work. A 20A DC-DC will likely pump 20A into the bank most of the time. So 1/2 hour driving x 20A = 10Ah returned to the battery bank. The price of this predictability (and other features) is... price. | ||
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+ | If you need predictable charging then DC-DC is likely the answer. | ||
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+ | ===== estimating combiner charging ===== | ||
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+ | This is the tough one. We know roughly where the charge rate will start out for discharged batteries (≤0.33C) but the taper complicates things. | ||
+ | **NOTE**: | ||
- | There are two main ways to charge from the alternator: | + | * **FLA** taper is steep; |
+ | * 100Ah x .12C = 12A. | ||
+ | * 0.5hours of driving x 12A = 6Ah replaced. | ||
+ | * **AGM** taper is more gradual, so charging currrent stays higher on short drives. It might only taper to 0.15C by the end of the drive. We might use 0.175C as our average rate. 8.75Ah replaced. | ||
+ | * **Lithium** has an odd taper because the charging voltage curve is not linear. | ||
+ | * in the broad " | ||
- | Combiners are simple connections, | + | ==== in the real world ==== |
- | T | + | In most installs |
- | DC-DC charging rates are more predictable because of how they work. A 20A DC-DC will likely pump 20A into the bank most of the time. So 3 hours driving x 20A = 60Ah returned to the battery bank. The price of this predictability (and other features) is... price. | + | |
+ | * combiner charging is commonly paired with solar charging (also highly variable!) | ||
+ | * alternator charging is often a backup or "nice when you can get it" charging source. | ||